Ceramic-Core Inductor Component

This application claims the benefit of U.S. Application No. 63/708,277, filed Oct. 17, 2024, the contents of which are incorporated by reference for all purposes as if fully set forth herein.

The present disclosure relates generally to non-magnetic inductor components and more particularly to ceramic-core inductor components for radio frequency (RF) applications and configurable for mounting on a printed circuit board.

Ceramic-core inductor components are commonly integrated with increasingly smaller electrical circuits and host devices for use in certain radio frequency (RF) applications where reduced size and performance are of paramount importance. Such applications include hand-held communication devices, laptop computers, military and commercial aircraft, and space vehicles among others. For these and other applications, ceramic-core inductors generally exhibit better performance than ferrite-core inductors. The improved performance is largely attributable to the low permeability of the ceramic-core. Ceramic-core inductors store energy more efficiently, have a higher quality (Q) factor, a higher self-resonant frequency (SRF) and better temperature stability than ferrite-core inductors. Nevertheless, there is an ongoing need for further performance improvements in ceramic-core inductor components.

Those of ordinary skill in the art will appreciate that the drawings are illustrated for simplicity and clarity and therefore may not be drawn to scale and may not include well-known features, that the order of occurrence of actions or steps may be different than the representative order described, that some or all of such actions or steps may be performed concurrently unless specified otherwise, and that the terms and expressions used herein have meanings understood by those of ordinary skill in the art except where a different meaning is specifically attributed to them.

The disclosure relates generally to ceramic-core inductor components for radio frequency (RF) applications having improved performance. The ceramic-core inductor components described herein are suitable for use in filters, low noise amplifiers (LNAs), power supplies, oscillators, impedance matching circuits, servos, and other controllers, among a variety of other electrical circuits. Such circuits are found in space and terrestrial communications systems, radar systems, as well as automotive, medical, industrial and consumer electronics, among many other systems and applications.

1 3 FIGS.- 100 110 120 The ceramic-core inductor components described herein generally comprise a conductive coil wound about a ceramic-core. In, a representative inductor componentcomprises a ceramic-coresupporting a conductive coilwound about a body portion of the ceramic-core, between first and second ceramic standoffs thereof. The conductive coil comprises end portions electrically connected to corresponding electrical terminals (also referred to herein as “terminations”) integrated with the ceramic-core. These and other aspects of ceramic-core inductor components are described further herein.

L L The ceramic-core inductor components described herein have a dielectric constant (K) selected to reduce parasitic loss (e.g., parasitic capacitance) thereby improving inductor performance. The improved performance is characterized by a higher quality (Q) factor and higher self-resonant frequency (SRF) than comparable prior art ceramic-core inductors. The Q factor is a ratio of inductive reactance to a resistance of the inductor, X/R, where the inductive reactance is a function of inductance L and parasitic capacitance. The higher SRF is attributable to lower parasitic capacitance.

The dielectric constant is a material characteristic considered in the design of capacitors, not inductors. The inventors of the ceramic-core inductors described herein have nevertheless recognized that the self-resonant frequency (SRF) of ceramic-core inductors has an inverse relation to the dielectric constant (κ) of the ceramic-core and that appropriate selection of the ceramic-core based on the κ value can improve inductor performance. Representative ceramic-core inductor components described herein having a κ value of 8 or less are shown to have improved quality (Q) factor and SRF compared to prior art ceramic-core inductors having higher κ values. Representative ceramic-core inductors and ceramic compositions therefor are described herein.

5 6 FIGS.- 5 FIG. 122 112 114 116 113 102 124 126 115 117 124 126 In, a representative ceramic-core blankcomprises a body portionbetween first and second flangesandradially extending beyond a peripheryof the body portion. Each flange or a portion thereof includes a mounting surface constituting a standoff for mounting on a host mounting surface. In, the standoffsandeach include a corresponding end surfaceandon which the electrical terminals can be located as described further herein. Alternatively, the terminations can be located on a portion of the ceramic-core apart from the standoffsand.

6 FIG. The body portion and the radial flanges can both have polygonal cross-sections, for example a square cross-section shown in. In other implementations, the body portion and the flanges can both have circular cross-sections, and one or more flat surfaces can be provided on each flange for surface mounting or for electrical terminals as described herein. Alternatively, the body portion can have a circular cross section and the flanges can have a polygonal cross-section. In still other implementations, the ceramic-core blank is devoid of flanges extending radially outwardly of the body portion.

7 FIG. 128 112 124 126 115 117 128 113 In, an alternative ceramic-core blankcomprises a body portionlocated between first and second flanges comprising corresponding standoffsandwith corresponding mounting surfacesand, respectively. The alternative ceramic-core blankcomprises a four-sided polygonal cross-section and the standoffs extend beyond a peripheral portionof at least one side of the body portion.

5 9 FIGS.- The ceramic-cores ofcan comprise other shapes and configurations and can be formed by isostatic or mechanical pressing, or molding among other known and future ceramic forming operations, before firing.

The constituents of the ceramic-core composition depend generally on the required performance characteristics of the inductor component. The ceramic-core can comprise one or more of calcium-strontium tungstate, magnesium silicate, magnesium aluminate, magnesium aluminum silicate, calcium silicate, zinc silicate, aluminum silicate or silica, or a combination of two or more thereof, alone or in combination with other elements or compounds. Each of the foregoing elements or compounds has a dielectric constant (κ) of 8 or less. Aluminum silicate, magnesium aluminum silicate, and silica each have a dielectric constant of 6 or less. Magnesium aluminum silicate and silica have a dielectric constant of 5 or less.

In a particular implementation, the ceramic-core comprises, by weight, more than five percent (5%) of each of the following: magnesium aluminum silicate; magnesium silicate; and magnesium aluminate. In a more particular implementation, the ceramic-core comprises, by weight, more than fifteen percent (15%) magnesium aluminum silicate, more than five percent (5%) magnesium aluminate, and more than ten percent (10%) magnesium silicate, wherein the ceramic-core has a dielectric constant of 6 or less. In these and other implementations, the ceramic-core can optionally comprise other constituents, for example fillers or additives.

In an alternative implementation, the ceramic-core comprises, by weight, each of the following: between 41-54% silicon dioxide; between 27-38% aluminum oxide; between 10-17% magnesium oxide, wherein the ceramic-core has a dielectric constant of 5 or less. Other components of this alternative composition can comprise as much as 12% tin oxide, as much as 7% titanium oxide, and as much as 2% lanthanum oxide, among other additives. These or other additives to the ceramic-core composition can slightly increase the dielectric constant, possibly greater than 5.

8 9 FIGS.- 5 7 FIGS.and 2 4 FIGS.- 2 3 FIGS.- 8 9 FIGS.- 8 9 FIGS.- 130 132 130 132 130 132 The conductive coil comprises end portions electrically connected to corresponding electrical terminals integrated with the ceramic-core. The terminals can be configured as metallized or other conductive pads located on corresponding standoffs or on other portions of the ceramic-core, depending on how the component will be electrically integrated with (e.g., mounted on) the host device. In, first and second terminalsandare formed on end surfaces (shown in) of first and second standoffs.illustrate different views of the electrical terminalsand. Each electrical terminal can optionally wrap around and cover a side wall portion of the corresponding standoff to increase the contact area between the terminals and the ceramic-core, as shown inand. In, the terminalsandon the end surfaces of the standoffs constitute mounting surfaces. Thus configured, the ceramic-core inductor component can be electrically and mechanically integrated with a host device (e.g., a PCB) by reflow or wave soldering or some other electrical and mechanical integration operation.

In other implementations, the electrical terminals can be located on a surface of the ceramic-core other than the mounting surface. Thus configured, the mounting surface of the ceramic-core inductor component can be mechanically fastened to the host device (e.g., by a bonding material) and the electrical terminals located on different portions of the ceramic-core can be electrically integrated with the host device by a wire bond, solder, or some other conductor-connecting means.

In one implementation, the electrical terminals comprise a conductive base-layer plated with one or more conductive outer layers. The base-layer can comprise silver or some other high conductivity metal or alloy. In one implementation, the base-layer comprises a silver (Ag) frit deposited onto select portions of the ceramic-core (e.g., the standoff mounting surfaces). Other conductors can be used alternatively. The base-layer can be applied to the ceramic-core in a dipping or other known or future operation.

An outermost conductive layer can be formed directly on the base-layer or on an intermediate conductive layer. The outermost conductive layer composition can be selected to improve solderability (e.g., improved wetting) and antioxidation, among other properties of the termination. In one implementation, the outermost conductive layer is tin (Sn) or a tin-based alloy (e.g., SnPb). Other conductors can be used alternatively. The conductive outermost layer can be applied to the base-layer or to the intermediate layer in an electroplating operation among other known or future processes.

In some implementations, an intermediate conductive layer is located between the base-layer and the outermost conductive layer to protect the base-layer. For example, the intermediate layer can have a higher melting temperature than the base-layer. In one implementation, the intermediate layer comprises copper (Cu). Alternatively, the intermediate layer can be nickel (Ni) or some other conductor or alloy. The conductive intermediate layer can be applied to the base-layer in an electroplating operation among other known or future processes.

In other implementations, the electrical terminals comprise a silver-platinum-palladium (AgPtPd) alloy deposited onto select portions of the ceramic-core. Other platinum group metals or alloys can be used alternatively. Representative low melting point solders developed for surface-mount ceramic component terminations comprising such alloys include solder type Sn62, among others. The electrical terminals can be applied to the ceramic-core in a dipping or other known or future operation.

4 FIG. 121 123 120 130 132 The conductive coil can comprise a solid or hollow-core wire. In one implementation, the conductive coil is formed from a solid copper wire, among other good conductors. In another implementation, the conductive coil comprises a non-copper (e.g., aluminum) inner-core plated with copper or silver. The wire can optionally comprise a non-conductive outer sheath, like enamel, for electrical insulation. The wire can be wound about the ceramic-core in a coil winding operation after terminal formation. End portions of the conductive coil can be electrically connected to corresponding terminals by a spot or other welding operation, soldering, wire bonding or some other electrical integration operation. In some implementations, the end portions of the conductive coil are flattened prior to electrical integration. In, each end portionandof the conductive coilis electrically integrated with corresponding terminalsandlocated on the end surface of the corresponding standoff.

2 FIG. 102 100 124 126 The ceramic-core inductor components described herein can be configured for surface mounting or other integration with the host device. In, the first and second standoffs are located to orient an axis of the conductive coil parallel to the mounting surfaceof the host when the ceramic-core inductor componentis mounted on the mounting surface. The first and second standoffsandare sized to space the conductive coil apart from the mounting surface when the ceramic-core inductor component is mounted on the mounting surface.

2 4 FIGS.- 100 136 In some implementations, the ceramic-core inductor component comprises a non-conductive handle to accommodate automated pick and place assembly and other component handling operations. The non-conductive handle covers at least a portion of the inductor component. In, the ceramic-core inductor componentscomprise a non-conductive handlelocated on a portion of the ceramic-core opposite the standoffs. In other implementations, the non-conductive handle covers all portions of the inductor component except for the electrical terminals. The non-conductive handle can comprise an epoxy, plastic, resin, or other non-conductive material. The non-conductive handle can be applied by a dipping, spraying or other application operation after assembly of the coil about the ceramic-core.

Representative dimensions for the ceramic-core inductor components described herein are depicted in Table I below. The “Size” refers to the length and width dimensions of the mounting surface area of the component. The sizes disclosed below are typical of surface-mount components and are not intended to limit the scope of the disclosure. In other implementations, the ceramic-core inductors described herein can be larger or smaller than the sizes depicted below, depending on electrical and performance requirements and integration constraints for the intended use case.

TABLE I Size Size Length Width Height Min Max Metric Imperial (mm) (mm) (mm) Inductance Inductance 1005 402 1 0.5 0.6 0.8 nH 1000 nH 1608 603 1.6 0.8 0.8 1 nH 3 μH 2012 805 2 1.25 1.4 1.8 nH 10 μH 2520 1008 2.5 2.02 1.8 3 nH 10 μH 3225 1210 3.06 2.4 1.9 3 nH 10 μH

The inductance of the ceramic-core inductor component is a function of the geometry of the coil (e.g., number of coil-turns, length, and cross-sectional area of the coil) as well as the magnetic permeability of the ceramic-core and neighboring materials. Thus, the range of inductance values for the ceramic-core inductor components described herein are generally constrained by the size of the component and the nature of the ceramic-core and surrounding materials. Typical minimum inductor values for the representative ceramic-core inductor component sizes in Table I range between 0.8 nH and 3 pH. However, the inductance can be larger or smaller, depending on electrical and performance requirements and integration constraints for the intended use case.

Table II below shows measured characteristics of a prior art 1 μH ceramic-core inductor and a 1 μH ceramic-core inductor having a dielectric constant of 5 or less according to the present invention. Both inductors have an inductance of 1 μH with a tolerance of 10% or less. The inductor according to the present invention has higher minimum and maximum Q factors, and a higher SRF than the prior art inductor. The Size represents the length and width dimensions (i.e., 2.5 mm by 2.0 mm) of the components.

TABLE II Inductance (nH) @ Q min @ SRF 1 μH Size 25 MHz 50 MHz Max Q (MHz) Prior art 2520 935 46 55 @ 122 MHz 395 Invention 2520 988 50 62 @ 110 MHz 405

11 FIG. 12 FIG. illustrates plots of measured Q factor versus frequency for the 1 μH ceramic-core inductors depicted in Table II. The higher Q factor of the ceramic-core inductor of the present invention is indicative of higher efficiency (i.e., reduced parasitic loss) than the prior art inductor and thus improved performance.illustrates plots of measured inductance versus frequency for the 1 pH ceramic-core inductors depicted in Table II.

Table III below shows measured characteristics of a prior art 470 nH ceramic-core inductor and a 470 nH ceramic-core inductor having a dielectric constant of 5 or less according to the present invention. Both inductors have an inductance of 470 nH with a tolerance of 5% or less. The inductor according to the present invention has higher minimum and maximum Q factors, and a higher SRF than the prior art inductor. The Size represents the length and width dimensions (i.e., 2.5 mm by 2.0 mm) of the components.

TABLE III Inductance (nH) @ Q min @ SRF 470 nH Size 25 MHz 100 MHz Max Q (MHz) Prior art 2520 452 57 66 @ 182 MHz 575 Invention 2520 464 63 70 @ 159 MHz 589

13 FIG. 14 FIG. illustrates plots of measured Q factor versus frequency for the 470 nH ceramic-core inductors depicted in Table III. The higher Q factor of the ceramic-core inductor of the present invention is indicative of higher efficiency (e.g., reduced parasitic loss) than the prior art inductor and thus improved performance.illustrates plots of measured inductance versus frequency for the 470 nH ceramic-core inductors depicted in Table III.

Table IV below shows measured characteristics of a prior art 12 nH ceramic-core inductor and a 12 nH ceramic-core inductor having a dielectric constant of 5 or less according to the present invention. Both inductors have an inductance of 470 nH with a tolerance of 5% or less. The inductor according to the present invention has higher minimum and maximum Q factors, and a higher SRF than the prior art inductor. The Size represents the length and width dimensions (i.e., 2.5 mm by 2.0 mm) of the components.

TABLE IV Inductance (nH) @ Q min @ SRF 12 nH Size 25 MHz 500 MHz Max Q (MHz) Prior art 2520 12 67  89 @ 1000 MHz >1000 Invention 2520 11.6 82 120 @ 1000 MHz >3000

15 FIG. 16 FIG. illustrates plots of measured Q factor versus frequency for the 12 nH ceramic-core inductors depicted in Table IV. The higher Q factor of the ceramic-core inductor of the present invention is indicative of higher efficiency (e.g., reduced parasitic loss) than the prior art inductor and thus improved performance.illustrates plots of measured inductance versus frequency for the 12 nH ceramic-core inductors depicted in Table IV.

While the disclosure and what is presently considered to be the best mode thereof has been described in a manner establishing possession and enabling those of ordinary skill in the art to make and use the same, it will be understood and appreciated that there are many equivalents to the representative embodiments described herein and that myriad modifications and variations may be made thereto without departing from the scope and spirit of the invention, which is to be limited not by the embodiments described, but by the appended claims and their equivalents.